The Four Values

In order for XP to be a viable discipline of development everyone who is involved in an XP project needs to buy into a common set of values that will permeate all the rules that make up the discipline. In XP there are the following four core values that enable it to work:

• Communication
• Simplicity
• Feedback
• Courage

Communication really means spreading the collective knowledge of the group around to all the members. Keeping the XP team small facilitates communication by keeping the number of lines of communication small. Pair programming and collective ownership of the code also facilitate communication by spreading the knowledge of the entire code base around the entire team. XP developers are encouraged to fix bugs they find and to redesign features to make them simpler (see below); this spreads knowledge of the code widely among the team.